The present invention relates generally to the connectorization of optical fibers and, more particularly, to multifiber connectors, installation tools and associated methods for validating optical fiber continuity during the connectorization process.
Although fiber optic connectors can generally be most efficiently and reliably mounted upon the end portions of optical fibers in a factory setting during the production of fiber optic cable, many fiber optic connectors must be mounted upon the end portions of optical fibers in the field. As such, a number of fiber optic connectors have been specifically developed to facilitate field installation. One advantageous type of fiber optic connector that is specifically designed to facilitate field installation is the UNICAM(copyright) family of fiber optic connectors provided by Siecor Corporation of Hickory, N.C. While the UNICAM family of fiber optic connectors includes a number of common features including a common splicing technique, the UNICAM family of fiber optic connectors has several different styles of connectors including UNICAM connectors adapted to be mounted upon a single optic fiber and UNICAM connectors adapted to be mounted upon two or more optical fibers, such as the MT-RJ UNICAM connector. See, for example, U.S. patent application Ser. No. 09/108,451 filed Jul. 1, 1998 and assigned to Siecor Corporation, which describes a multifiber connector, such as an MT-RJ UNICAM connector, adapted to be spliced onto the end portions of a plurality of optical fibers. The contents of this patent application are hereby incorporated by reference in their entirety.
By way of example of an advantageous fiber optic connector designed for field installation, FIG. 1 depicts an MT-RJ UNICAM(copyright) connector 10. The connector generally includes a ferrule 12 defining one or more bores for receiving respective optical fiber stubs. The optical fiber stubs are preferably sized such that one end of the optic fiber stubs extends rearwardly beyond the ferrule. The MT-RJ UNICAM(copyright) connector also includes splice components, at least one of which defines a groove for receiving an end portion of each optical field fiber upon which the fiber optic connector is to be mounted. In order to mount the fiber optic connector upon optical field fibers, the splice components are positioned proximate the rear end of the ferrule, such that the end portions of the optical fibers stubs that extend rearwardly beyond the ferrule are disposed within the respective grooves defined by the splice components. Thereafter, end portions of the optical field fibers can also be inserted into the respective grooves defined by the splice components. By inserting the optical field fibers into the grooves defined by the splice components until respective end portions of the optical fiber stubs and the optical field fibers make contact, optical connections can be established between respective pairs of the optical fiber stubs and the optical field fibers. In this regard, the contact between the end portions of the optical fiber stubs and the optical field fibers establishes optical continuity between respective pairs of the optical fiber stubs and the optical field fibers. The splice components can then be actuated, such as by means of a cam member 20, in order to force the splice components together and to secure the end portions of the optical fiber stubs and the optical field fiber in position within the respective grooves defined by the splice components.
In order to facilitate the connectorization of optical fibers in the field, installation tools have also been developed. For example, U.S. Pat. No. 5,040,867 to Michael de Jong et al. and U.S. Pat. No. 5,261,020 to Michael de Jong et al. describe installation tools for facilitating the connectorization of optical fibers in the field. In addition, a UNICAM(copyright) installation tool kit is provided by Siecor Corporation of Hickory, N.C., to facilitate the mounting of the UNICAM(copyright) family of connectors upon the end portions of optical field fibers in the field. An installation tool holds a number of components of the fiber optic connector including the ferrule and the splice components while the optical field fibers are inserted into the fiber optic connector and aligned with the respective optical fiber stubs.
In this regard, one conventional installation tool includes a base and a tool housing mounted upon the base. The installation tool also includes an adapter disposed within the tool housing. The adapter has a first end for engaging the fiber optic connector that is to be mounted upon the optical field fibers and an opposed second end that is a dust cap. The installation tool also includes a bias member mounted within the tool housing that engages a shoulder defined between the first and second ends of the adapter in order to secure the adapter in position within the tool housing. Typically, the bias member includes a slide member slidably connected to the tool housing and a biasing element, such as a spring, for urging the slide member into engagement with the shoulder defined by the adapter. The slide member generally includes an engagement portion having a U-shape through which the second end of the adapter extends. In addition, a conventional slide member includes a base portion disposed between the tool housing and the base and connected to the engagement portion by means of a connecting element that extends through a lengthwise extending slot defined by the tool housing. Thus, the movement of the connecting element through the slot defined by the tool housing guides the corresponding movement of the slide member in a lengthwise direction relative to the tool housing in order to engage the shoulder defined by the adapter, thereby securing the adapter in position within the tool housing.
In order to mount the fiber optic connector upon the end portions of the optical field fibers, the fiber optic connector is mounted within the installation tool. In particular, the forward end of the fiber optic connector is engaged by the first end of the adapter which, in turn, is secured within the tool housing once the slide member is biased into engagement with the shoulder defined by the adapter. The end portions of the optical field fibers are then inserted into the rear end of the fiber optic connector and the splice components are subsequently actuated, such as by being cammed together, in order to secure the optical field fibers relative to respective optical fiber stubs. The crimp tube 24 of the fiber optic connector is then crimped about the optical field fibers and, in some applications, a crimp band 26 is crimped to the strength members surrounding the optical field fibers in order to provide strain relief and otherwise protect the splice connections of the optical field fibers and the optical fiber stubs.
Once fiber optic connectors have been mounted upon the opposed end portions of the optical field fibers, the resulting fiber optic cable assembly is preferably tested end-to-end. Among other things, this testing is designed to insure that optical continuity has been established between the optical fiber stubs and respective optical field fibers. While fiber optic cables can be tested in different manners, one test involves the introduction of light having a predetermined intensity into each optical fiber stub. By measuring the light following its propagation through the fiber optic cable assembly and, more particularly, by measuring the insertion loss and back reflectance onto each optical fiber stub with a power meter, the continuity of each optical field fiber and the respective optical fiber stub can be determined. If the testing indicates that the optical fibers are not sufficiently continuous, the technician must either scrap the entire fiber optic cable assembly or, more commonly, replace one or both fiber optic connectors in an attempt to establish the desired continuity. In order to replace the fiber optic connectors, a technician generally removes, i.e., cuts off, one of the fiber optic connectors and repeats the connectorization process described above by mounting a new fiber optic connector within the installation tool and inserting the optical field fibers into the new fiber optic connector. Once the new fiber optic connector has been mounted upon the end portions of the optical field fibers, the new fiber optic connector is removed from the installation tool and the fiber optic cable assembly is again tested. If the optical fibers are still not sufficiently continuous, the fiber optic connector mounted upon the other end of the fiber optic cable assembly is typically removed and replaced as described above, prior to further testing of the resulting fiber optic cable assembly.
While fiber optic connectors and associated installation tools have been developed to facilitate the mounting of the fiber optic connectors upon the end portions of optical field fibers in the field, conventional field connectorization techniques can be quite time consuming and expensive. In this regard, since the continuity testing is not performed until after the fiber optic connectors have been completely mounted to the optical field fibers, one or both of the fiber optic connectors must typically be replaced if the testing indicates a discontinuity between the optical field fibers and the respective optical fiber stubs. This process not only requires additional time to effect the reconnectorization, but also increases the cost of the resulting fiber optic cable assembly by causing a number of potentially functional fiber optic connectors to be disadvantageously scrapped since the testing generally does not indicate which of the fiber optic connectors should be replaced. In this regard, the technician generally randomly picks one of the fiber optic connectors to replace, thereby insuring that a fiber optic connector that has been appropriately mounted upon the optical field fibers is replaced almost half of the time.
The reconnectorization of one or both ends of a fiber optic cable assembly is particularly troublesome for fiber optic cable assemblies that include a plurality of optical field fibers. In this regard, if the testing indicates a discontinuity involving any one of the optical field fibers, the fiber optic connectors mounted upon one or both ends of the fiber optic cable assembly must generally be replaced, even if the other optical field fibers and the optical fiber stubs have the desired continuity.
In order to facilitate continuity testing while the fiber optic connector remains mounted within the installation tool, Siecor Corporation previously developed a modified installation tool for a single fiber CamLite(trademark) ST connector that permitted continuity testing. The installation tool included an adapter having opposed first and second ends, the first end of which was adapted to engage a single fiber CamLite ST connector. In order to test the continuity of the optical fiber, a laser, such as an HeNe gas laser, was provided that delivered red light to the optical fiber stub of the single fiber CamLite ST connector. More particularly, the red light was delivered via an optical fiber upon which another ST connector was mounted. This other ST connector was, in turn, inserted into the second end of the adapter such that the red light was delivered to the optical fiber stub of the single fiber CamLite ST connector. By monitoring the glow emanating from the end portion of the optical fiber stub within the fiber optic connector through a translucent connector body, the technician could determine when contact was established between the optical fiber stub and the optical field fiber based upon the dissipation of the glow, i.e., continuity is presumed to have been established once the glow dissipates. Thereafter, the cam member of the single fiber CamLite ST connector could be actuated to fix the relative positions of the optical field fiber and the optical fiber stub prior to making a final check of continuity.
While the installation tool developed by Siecor Corporation for the single fiber CamLite ST connector advantageously monitored the continuity of an optical field fiber and an optical fiber stub while the single fiber CamLite ST connector remained within the installation tool, this installation tool provided no mechanism for uncamming and repositioning the optical field fiber relative to the optical fiber stub if the continuity was inadequate after cam actuation. As such, the fiber optic connector would still have to be removed from the end portion of the optical fiber and replaced by a new single fiber CamLite ST connector if testing subsequently determined that the optical field fiber and the optical fiber stub were actually discontinuous. In addition, the modified installation tool developed by Siecor Corporation was only capable of mounting a fiber optic connector upon a single optical fiber and, more particularly, mounting a CamLite ST connector upon a single optical fiber and did not permit multifiber connectors to be mounted upon the end portions of a plurality of optical field fibers. As such, improved techniques for mounting multifiber connectors upon optical field fibers in the field and for testing the resulting fiber optic cable assembly are desired in order to reduce the overall time required for the mounting and testing procedures and to correspondingly reduce the cost of the resulting fiber optic cable assembly.
Methods are therefore provided according to the present invention for validating the continuity of one or more optical fibers upon which a fiber optic connector is mounted. According to one embodiment, the fiber optic connector can be mounted upon an optical field fiber by actuating a cam mechanism to secure the optical field fiber in position relative to an optical fiber stub. If subsequent evaluation indicates that the continuity of the optical field fiber and the optical fiber stub is unacceptable, the cam mechanism can be deactuated, the optical field fiber can be repositioned and the cam mechanism can be reactuated without having to remove and replace the fiber optic connector. In order to determine if continuity has been established between the optical field fibers and respective optical fiber stubs, a method is also provided that introduces light into at least one of each pair of optical field fibers and optical fiber stubs and that only secures the position of each optical field fiber relative to the respective optical fiber stub once the glow associated with each pair of optical field fibers and optical fiber stubs dissipates, which dissipation indicates the establishment of continuity. An improved multifiber connector and installation tool are also provided to facilitate the establishment and validation of the continuity of optical field fibers and optical fiber stubs in order to reduce the time and cost required to connectorize optical field fibers in the field.
According to one advantageous embodiment, a method is provided for validating the continuity of an optical fiber upon which a fiber optic connector is mounted. In this regard, the fiber optic connector includes a ferrule defining at least one bore extending between opposed front and rear faces, an optical fiber stub extending through the bore and beyond the rear face of the ferrule, and a cam mechanism. According to this embodiment, an optical field fiber is advanced into the fiber optic connector while light is introduced into at least one of the optical field fiber and the optical fiber stub. So long as the optical field fiber and the optical fiber stub are discontinuous, a glow will emanate from an end portion of the optical field fiber or the optical fiber stub into which light is introduced. The glow is monitored while the optical field fiber is advanced into the fiber optic connector and further advancement of the optical field fiber is halted once the glow dissipates. The cam mechanism is then actuated to secure the optical field fiber in position relative to the optional fiber stub. Once the cam mechanism has been actuated, the continuity of the optical field fiber and the optical fiber stub is evaluated, preferably while the fiber optic connector remains within the installation tool. If the continuity of the optical field fiber and the optical fiber stub is unacceptable, the cam mechanism is deactuated. The optical field fiber is then repositioned relative to the optical fiber stub. In this regard, the optical field fiber is typically cleaved and cleaned prior to the repositioning to improve the resulting connection. Once the optical field fiber has been repositioned, the cam mechanism is reactuated. The evaluation of the continuity of the optical field fiber and the optical fiber stub as well as any necessary deactuation of the cam mechanism, repositioning of the optical field fiber and reactuation of the cam mechanism can be repeated as necessary to achieve continuity. Once acceptable continuity is obtained, the fiber optic connector can be crimped onto the optical field fibers and, more typically, to the strength members surrounding the optical field fibers.
By permitting repeated repositioning of the optical field fiber prior to crimping the fiber optic connector onto the optical field fibers, the method of this embodiment prevents otherwise acceptable fiber optic connectors from being replaced in an attempt to establish continuity between optical field fibers and optical fiber stubs. Thus, the total time required to mount the fiber optic connectors upon the optical field fibers and to validate the resulting continuity of the optical fibers is decreased according to the method of this embodiment of the present invention. Correspondingly, the cost of the resulting fiber optic cable assembly, on average, is also decreased since fewer fiber optic connectors are removed and scrapped.
In order to permit the glow emanating from the end portion of at least one optical fiber stub or optical field fiber that is indicative of a discontinuity to be viewed, a multifiber connector is also provided according to another embodiment of the present invention. The multifiber connector of this embodiment includes a multifiber ferrule extending lengthwise between opposed front and rear faces for receiving a plurality of optical fiber stubs. The multifiber connector also includes splice components positioned proximate the rear face of the multifiber ferrule for aligning a plurality of optical field fibers with respective ones of the plurality of optical fibers stubs. The multifiber connector also includes a cam mechanism for urging the splice components together to operably interconnect respective pairs of the optical field fibers and the optical fibers stubs. According to this embodiment of the present invention, at least one of the cam mechanism and the splice components is translucent such that the glow emanating from therewithin that is indicative of a discontinuity between at least one pair of optical field fibers and optical fibers stubs is externally visible.
In one embodiment, the cam mechanism of the multifiber connector includes a sleeve in which the splice components are disposed. The sleeve of this embodiment also defines a window through which the splice components are exposed. In addition to the sleeve, the cam mechanism of this embodiment includes a cam member disposed upon the sleeve for engaging the splice components via the window defined by the sleeve. As such, movement of the cam member relative to the sleeve urges the splice components together. In this embodiment, the cam member is typically translucent. As such, the multifiber connector of this embodiment of the present invention permits the connectorization process to be monitored to ensure that continuity is established between each optical field fiber and the respective optical fiber stubs prior to actuating the cam mechanism to secure the optical field fibers in position relative to the respective optical fiber stubs.
An installation tool is also provided according to another embodiment of the present invention for mounting the fiber optic connector upon one or more optical field fibers. The installation tool of this embodiment is capable of being converted between a first configuration that facilitates validation of the continuity of the optical fibers and a second configuration in which the continuity of the optical fibers is untested.
According to this embodiment, the installation tool includes a tool housing extending lengthwise between first and second opposed ends. The installation tool also include first and second adapters capable of being alternately mounted within the tool housing to configure the installation tool in the first and second configurations, respectively. The first adapter has a first end adapted to engage the fiber optic connector that is being mounted upon the optical field fiber and an opposed second end adapted to engage a fiber optic connector that is mounted upon another optical fiber that delivers light for continuity testing. While the second adapter also has a first end adapted to engage the fiber optic connector that is mounted upon the optical field fiber, the second end of the second adapter serves as a dust cap. Each adapter further defines a shoulder between the opposed first and second ends. The installation tool of this embodiment of the present invention also includes first and second bias members capable of being alternately mounted within the tool housing to configure the installation tool in the first and second configurations, respectively. The bias members are adapted to be biased into engagement with the shoulder defined by the respective adapter to thereby secure the respective adapter in position within the tool housing.
According to this embodiment of the present invention, the first and second adapters and the first and second bias members can be interchanged to convert the installation tool between the first and second configurations without otherwise disassembling the installation tool. In this regard, the first adapter and the first bias member can be mounted within the tool housing such that the installation tool has the first configuration that permits testing of the continuity of the optical fibers upon which the fiber optic connector is mounted. Alternatively, the second adapter and the second bias member can be mounted within the tool housing such that the installation tool has the second configuration that does not support continuity testing, but appears and functions in the same manner as a conventional installation tool.
According to this embodiment of the present invention, each bias member preferably includes a slide member and a biasing element for urging the respective slide member into engagement with the shoulder defined by the respective adapter to thereby secure the respective adapter and connector in position within the tool housing. Moreover, each slide member can include an engagement portion capable of being disposed within the tool housing for engaging the shoulder defined by the respective adapter and a base portion disposed on the opposite side of the tool housing from the engagement portion. In addition, each slide member can include a removable connector interconnecting the engagement portion and the base portion. The removable connector extends through a slot defined by the tool housing such that the removable connector rides within the slot as the slide member moves relative to the tool housing. Each slide member preferably includes a common base portion. As such, by removing the removable connector, the engagement portions of the first and second adapters can be interchanged and mounted to the common base portion without otherwise disassembling the installation tool.
Accordingly, the installation tool can be configured to support continuity testing of a fiber optic connector that remains mounted within the installation tool. Alternatively, the installation tool can be configured as a conventional installation tool that does not support continuity testing. By permitting continuity testing without removing the fiber optic connector from the installation tool, however, the installation tool of this embodiment of the present invention further facilitates the rapid repositioning of the optical field fibers relative to the optical fiber stubs in order to achieve continuity without having to scrap the fiber optic connector as required by conventional techniques.